Combination seat belt retractor mechanism

ABSTRACT

A combination seat belt retractor particularly useful for motor vehicles is described. The seat belt retractor according to this invention converts between an emergency locking retractor which locks only when the vehicle is subjected to a deceleration level above a predetermined level to an automatic locking mode wherein the seat belt webbing cannot be withdrawn from the retractor. The convertible feature is particularly advantageous since an emergency locking retractor does not provide the desired firm positioning of child restraint systems. The emergency locking retractor, however, has advantages in terms of occupant comfort and convenience since they permit free movement of the occupants within the vehicle. In accordance with this invention, the retractor is converted to the automatic locking mode by first fully withdrawing the seat belt webbing therefrom. Such action causes a switching lever to force a leaf spring in a position against the retractor locking bar. When, however, a predetermined amount of seat belt webbing is returned upon the retractor spool, the leaf spring returns to its normal position, thereby restoring emergency locking operation to the retractor.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a motor vehicle seat belt retractor andparticularly to a retractor which can be operated both as an emergencylocking retractor or an automatic locking retractor.

Most motor vehicles are equipped with seat belt systems which act torestrain the occupants when the vehicle is subjected to high rates ofdeceleration which may occur, for example, during a motor vehiclecollision. Many seat belt retractors are of the so-called emergencylocking variety. These retractors employ an inertia sensitive actuatorwhich prevents seat belt webbing from being withdrawn from the retractorwhen the vehicle is subjected to deceleration forces above apredetermined level, thereby restraining the vehicle occupant. Duringnormal operating circumstances, however, the seat belt webbing may befreely withdrawn from the retractor, enabling freedom of movement by thevehicle occupants.

Another type of seat belt retractor is often referred to as an automaticlocking retractor. When using these retractors, the seat belt webbing isfully withdrawn from the retractor and, as webbing is thereafterretracted within the retractor, a locking bar engages sprockets withinthe retractor thus preventing withdrawal. These retractors therefore,act as a one-way clutch once the webbing is fully withdrawn, permittingwebbing to be retracted within the retractor but not withdrawn. When,however, the seat belt is unfastened and the webbing is fully retractedwithin the retractor, the webbing can again be withdrawn.

The emergency locking retractor design has many advantages in terms ofoccupant comfort and convenience, since they permit free movement of theoccupants until deceleration forces above a predetermined level aresensed. Emergency locking retractors, however, have been foundundesirable when used to fasten a child restraint system within thevehicle. For this application, it is desirable that the seat belt systemfirmly and securely anchor the child restraint system to the vehicle.Since automatic locking retractors do not permit free withdrawal ofwebbing, they are preferable for anchoring a child restraint systemwithin the vehicle.

Due to the need to provide adult occupant comfort and convenience, andthe need to securely fasten child restraint systems within vehicles, itis desirable to provide a combination seat belt retractor which may beconverted between emergency locking operation and automatic lockingoperation in accordance with the needs of the user. It is therefore aprincipal object of this invention to provide such a combination seatbelt retractor. It is a further object of this invention to provide acombination emergency locking and automatic locking retractor which iseasily switched between operational modes. It is yet another object ofthis invention to provide a combination seat belt retractor which issimple in design and inexpensive. It is yet another object of thisinvention to provide a combination retractor having an automatic lockingmechanism which is independent of the emergency locking inertiaactuator, thereby not adversely affecting the reliability of theemergency locking feature of the retractor.

The above principal objects of this invention are achieved by providingan emergency locking retractor having, in addition, a two-position leafspring which, in one position, acts to directly bias the retractorlocking bar against the toothed sprockets of the retractor spool,thereby causing the retractor to operate in an automatic locking mode.The retractor according to this invention further includes a switchinglever which moves the leaf spring to the automatic locking position whenthe seat belt webbing is fully withdrawn from the retractor. Theretractor is designed such that when the spool is nearly fully wrappedwith seat belt webbing, the leaf spring is pushed to a first normalposition wherein it no longer biases the locking bar, thus returning theretractor to emergency locking operation.

Additional benefits and advantages of the present invention will becomeapparent to those skilled in the art to which this invention relatesfrom the subsequent description of the preferred embodiments and theappended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a combination seat belt retractor according tothis invention;

FIG. 2 is a side view of the combination seat belt retractor accordingto this invention shown by FIG. 1;

FIG. 3 is a plan view of the combination seat belt retractor shown byFIG. 1;

FIG. 4 is a plan view of the leaf spring which is incorporated into thecombination seat belt retractor according to this invention; and

FIG. 5 is a side view of the leaf spring shown by FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

A combination seat belt retractor according to this invention is shownassembled in FIGS. 1, 2 and 3, and is generally designated there byreference character 10. Retractor assembly 10 includes retractor frame12 to which rotatable spool 14 is mounted. Spool 14 includes a beltsupport shaft 16 terminating laterally in a pair of radially extendingtoothed sprockets 18 and 20. Torsion spring assembly 22 acts upon beltsupport shaft 16 to rotatably bias spool 14 so that a belt webbingretracting force is applied when webbing 24 is withdrawn from retractor10. One end of seat belt webbing 24 is attached to belt support shaft 16and becomes rolled onto spool 14 as it is rotated. Retractor frame 12includes one or more mounting holes 26 for fasteners which permit secureattachment of retractor 10 to the associated vehicle. Locking bar 28 isparticularly shown by FIGS. 1 and 2 and is movable between a firstnormal position to a second engaging position wherein the locking barengages one of the teeth of toothed sprockets 18 and 20. Locking bar 28is caused to move between the position shown by FIGS. 3 and 4 by inertiasensitive actuator 30 which includes; housing 32 attached to frame 12,and internally disposed weighted element 34. Weighted element 34 movesto a tilted position once combination retractor assembly 10 (and theassociated motor vehicle) are exposed to deceleration forces above apredetermined level (or when retractor frame 12 is tilted from itsinstalled position). Once weighted element 34 is caused to move to atilted position, locking lever 36 becomes raised due to contact betweenthe weighted element and lug 38 of the locking lever. Locking lever 36rotates about pivot 40 between the normal and engaged positions.Retractor frame is preferably enclosed by trim cover 72.

FIG. 2 illustrates the normal position of the components of inertiasensitive actuator 30. When, however, weighted element 34 moves toward atilted position, locking lever 36 is caused to rotate in a clockwisedirection, with respect to the orientations shown by FIG. 2. Onceslightly rotated, actuator pawl 42 of locking lever 36 engages a toothof spur gear 44 which is also rotatable with spool 14. Rotation of spool14 causes continued rotation of locking lever 36 until locking bar pawl37 contacts the underside of locking bar 28 urging it into engagementwith a tooth of toothed sprockets 18 and 20. Actuator pawl 42 and spurgear 44 are provided to augment the rotational urging forces applied tolocking lever 36 as weighted element 34 becomes tilted. Suchaugmentation results in improved reliability and accuracy of retractorlocking and provides positive engagement between locking bar 28 andtoothed sprockets 18 and 20.

The foregoing description describes components of an emergency lockingretractor design known to the prior art. In accordance with thisinvention, retractor 10 is also provided with leaf spring 46 andswitching lever 48. Leaf spring 46 is shown in detail by FIGS. 4 and 5and includes two end tabs 50 and 52, and offset portion 54. Theinstallation of leaf spring 46 within retractor 10 is best shown withreference to FIG. 2. End tab 50 of leaf spring 46 is caused to engageupset slot 56 formed within the lower portion of retractor frame 12.Leaf spring end 52 is inserted within slot 58, formed within crossmember 60 which is attached to retractor frame 12. As is shown by FIG.2, leaf spring 46 is designed to occupy two positions, a first normalposition illustrated by the lower phantom line position of leaf spring46 designated by reference character 62, or a second position 64 shownin a displaced upward position. Leaf spring 46 is caused to assumeeither position 62 or 64 and snap between such positions by spacingslots 56 and 58 a distance apart less than the length of leaf spring 46between end tabs 50 and 52. Such spacing prevents leaf spring 46 fromoccupying a position intermediate of positions 62 and 64 withoutexternal forces being applied to the spring. When in second position 64,leaf spring 46 contacts locking bar 28 urging it toward engagement witha tooth of toothed sprockets 18 and 20. When leaf spring 46 is in secondposition 64, combination seat belt retractor 10 functions as anautomatic locking retractor since seat belt webbing 24 cannot bewithdrawn from retractor 10 due to engagement between locking bar 28 andtoothed sprockets 18 and 20. When leaf spring 46 is in its firstposition 62, however, normal movement of locking bar 26 in response toinertia sensitive actuator 30 is restored.

Leaf spring 46 is caused to move from position 62 to 64 by the action ofswitching lever 48. Switching lever 48 is pivotably mounted to crossmember 60 and has two terminal ends, 66 and 68. End 66 is positioned tocontact an edge 70 of seat belt webbing 24 presented when the webbing isfully withdrawn from spool 14. Alternately, switching may be achieved bya folded over position of webbing 24 or other means of engagingswitching lever 48. When such contact occurs, switching lever 48 iscaused to rotate about locking bar 28 such that end 68 contacts leafspring 46 urging it toward second position 64, thus changing theretractor into the automatic locking mode as explained above. When,however, seat belt webbing 24 is returned onto spool 14, the wrapseventually come in driven contact with leaf spring 46 until the leafspring is caused to return to first normal position 62, at which pointthe retractor is switched into the emergency locking mode.

In operation, when the user wishes to convert retractor 10 to theautomatic locking mode, seat belt webbing 24 is fully withdrawn from theretractor, whereupon edge 70 engages switching lever end 66 which causesleaf spring 46 to assume position 64, thus causing the retractor toswitch into the automatic locking mode. After the seat belt latch plateis fastened to the seat belt buckle, the child restraint system issecurely fastened within the motor vehicle. When, however, the seat beltbuckle is unfastened, seat belt webbing 24 returns to retractor 10 tothe extent that leaf spring 46 is caused to move to position 62, therebyreturning the retractor to the emergency locking mode. It is desirableto cause such switching to occur at a point where seat belt webbing 24is nearly fully retracted within retractor 10, therefore avoiding areturning to emergency locking mode while the child restraint system isfastened within the vehicle. When in use by an adult occupant, retractor10 will normally remain in the emergency locking mode since most adultoccupants do not fully withdraw seat belt webbing from a retractor inorder to fasten the belt.

In order to not detract from the reliability of inertia sensitiveactuator 30, leaf spring 46 and switching lever 48 operate independentlyfrom the inertia sensitive actuator since they act directly upon lockingbar 28. The design according to this invention further provides apositive indication to the motor vehicle user regarding which mode ofoperation retractor 10 is in. While in the automatic locking mode,retracting of belt 24 causes an audible clicking sound as locking bar 28moves along the teeth of tooth sprockets 18 and 20.

While the above description constitutes the preferred embodiments of thepresent invention, it will be appreciated that the invention issusceptible to modification, variation and change without departing fromthe proper scope and fair meaning of the accompanying claims.

What is claimed is: .[.1. A seat belt retractor which may be operatedeither as, an emergency locking retractor which prevents seat beltwebbing from being withdrawn when the retractor is subjected todeceleration above a predetermined level, or as an automatic lockingretractor which acts to retract said webbing but does not permitsubstantial withdrawal of said webbing comprising; .Iadd.11. In a motorvehicle seat belt retractor which may be operated either as an emergencylocking retractor which prevents seat belt webbing from being withdrawnwhen the retractor is subjected to deceleration above a predeterminedlevel, or as an automatic locking retractor which acts to retract saidwebbing but does not permit substantial withdrawal of said webbing,including a retractor frame, a spool rotatable within said frame andhaving a spindle upon which said webbing is wrapped and a pair oftoothed sprockets on opposite ends thereof, a locking bar engageablewith said toothed sprockets for restricting withdrawal of said webbingfrom said spool, and an inertia sensitive actuator acting upon saidlocking bar to cause engagement of said locking bar with said toothedsprockets when a deceleration of said vehicle above said predeterminedlevel is sensed, the improvement comprising:a leaf spring positionedbetween said toothed sprockets and having two ends and a center portionbetween said ends, each of said ends being mounted to said retractorframe at attachment points fixed with respect to said retractor frameand separated by a distance less than the free length of said spring,said spring being movable between a first state wherein said springcenter portion is deflected away from said spool and disengaged fromsaid locking bar wherein said locking bar is permitted to operate solelyin response to said internal sensitive actuator whereby said retractoroperates as an emergency locking retractor, and a second state whereinthe center portion of said spring is deflected toward said spool andacts by direct contact with said locking bar biasing said locking barinto engagement with said toothed sprockets causing said locking bar toengage with said toothed sprockets to engage the teeth of said sprocketsto restrict withdrawal of said webbing while allowing said locking barto ride over said teeth upon retraction of said webbing whereby saidretractor operates as an automatic locking retractor; and a web sensinglever pivotably mounted to said retractor frame and defining first andsecond arms on either side of said pivot axis, said lever beingpivotable between a first position and a second position, in said secondposition said first arm engaging said spring center portion and forcingsaid spring into said second state, said second arm positioned to engagesaid webbing when substantially all of said webbing has been withdrawnfrom said spool causing said lever to move to said second positionthrough contact with said webbing, and when said lever is in said secondposition and said webbing is being retracted onto said spool, saidspring is oriented such that when the diameter of the total wraps ofwebbing on said spool reaches a predetermined diameter, said wrapsdirectly contact said spring center portion forcing said spring toswitch from said second state to said first state. .Iaddend. .Iadd.12.The seat belt retractor of claim 11 wherein said leaf spring ends aretapered and each of said ends engage notches formed by said retractorframe at said mounting points. .Iaddend. .Iadd.13. The seat beltretractor of claim 12 wherein one of said notches is formed by a crossmember component of said retractor frame. .Iaddend. .Iadd.14. The seatbelt retractor of claim 11 wherein said leaf spring further forms anoffset adjacent one of said ends. .Iaddend. .Iadd.15. The seat beltretractor of claim 11 wherein said pivot axis for said web sensing leveris parallel to the axis of rotation of said spool. .Iaddend. .Iadd.16.The seat belt retractor of claim 11 wherein said spring is unstable atintermediate positions between said first and second states and isstable at either of said first and second states. .Iaddend. .Iadd.17.The seat belt retractor of claim 16 wherein said spring assumes anarcuate configuration in both of said first and second states such thatsaid center section of said leaf spring is disposed on one side of astraight line between said spring ends in said first state and on anopposite side of said line in said second state and said spring centerportion intersecting said line when said spring is in an intermediatestate between said first and second states. .Iaddend. .Iadd.18. The seatbelt retractor of claim 11 wherein when said spring is in said secondstate acting upon said locking bar, retraction of said webbing onto saidspool causes said locking bar to ratchet along said toothed sprocketsagainst the biasing force exerted by said leaf spring. .Iaddend.